Conventional steering wheels in vehicle present a bimanual manipulandum with variable locations to grasp a wheel in different situations. Bimanual steering technique is critical for driving safety. However, in contrast to airbags, the capability of detecting the driver's hands position during vehicle operation is not yet a prerequisite for the steering wheel design and manufacture. Nevertheless, increasing functionality of steering wheels and driving safety is of great interest in an automotive industry. For this reason, our goal is to increase functionality of the steering wheel covering by optimizing configuration of the cover assembly as a cost effective and informative surface for enabling driver interaction with in-car installed systems and devices.
Different solutions for hands position detection on the steering wheel have been considered and disclosed (e.g., U.S. Pat. No. 8,564,424-B, U.S. Pat. No. 7,321,311-B, US-2011-246028-A). However, these solutions are based on a sensor array incorporated into the covering or directly into the steering wheel body. Multiple sensors should have a wireless connection with a signal processor. Such an embodiment would be too expensive considering it is only targeted at capturing hands position. Wired sensor network is also expensive for manufacturing when motivated exclusively to realize the goal of hands position detection.
The sensors embedded or/and coupled with a vehicle steering wheel can detect biological parameters (vital sign related) of driver. For example, there is disclosed a sensor assembly mounted in the steering wheel (e.g., US-2011-125002-A, US-2011-245643-A, WO-2007-066513-A, WO-2013-076018-A, DE-10-2006-025852-A, JP-2009-045077-A). The sensor assembly includes electrodes configured to measure biological parameters of a driver in the vehicle such as heart rate, skin capacitance, skin temperature, respiration rate, and other parameters utilized to determine a driver's state or condition. However, the configuration of electrodes and measurement technique (e.g., for heart rate) requires that both driver's hands grasp the pair of electrodes placed in opposite segments of the wheel, simultaneously. This way of measurement of a biological parameter cannot be applicable in many situations for safety driving.
WO-2013-076018-A discloses optical sensors and conductive electrodes arranged on a steering wheel in specific locations to detect heart/respiration activity or/and ECG signals. The sensor surface area is formed by the actuation surface of a push-button switch that can be a shifting paddle for a gearshift transmission. The specific location of sensors can have an impact on the natural activity of the driver and prevent continuous monitoring of biological informative parameters.
To continuously detect the heart rate even if a driver operates a steering wheel with one hand, ECG-related dielectric potential generated between a steering electrode and a reference electrode due to press contact with the human body may be measured (e.g., JP-2009-142576-A, US-2013-022209-A). The reference electrode can be installed on the upper-part of seat while the lower-part seat would be grounded, on the backrest of the seat or arranged on an arbitrary location. However, these solutions cannot guarantee a compensation of a local muscle activity generated by fingers/hand squeezing the steering wheel, as this local activity does not present under the reference electrode.
Another functionality that can be integrated with the steering wheel is a tactile input and feedback techniques. US-2012-150388-A proposes an array of vibration sensors fixed to a steering wheel to realize a pie-like menu of commands for interaction with in-car installed mobile devices such as radio, cruise control, phone and others by tapping a particular section of the steering wheel. As it was already discussed in relation to a sensor array for the hands position detection, manufacturing multi-function steering wheels is expensive because of the complexities of manufacturing caused by sensor arrangement and their cabling, even with an intermediate micro-controller processing the information collected by distributed sensors and mounted in/near air bag.
Tactile input (rotary control knobs and buttons) can also be accompanied with a vibration-based tactile feedback (e.g., U.S. Pat. No. 8,364,342-B). Tactile/haptic feedback to warn of collision detection was disclosed (e.g., U.S. Pat. No. 6,812,833-B). The tactile feedback mechanism was adapted to provide a tactile response upon detection of a signal from the vehicle proximity sensor system of the presence of a second vehicle. Moreover, vibrators affixed to a steering wheel can be used for getting rid of stress while driving (e.g., JP-2006-056494-A, US-2002-162416-A). However, vibration for stress relief should not distract and still be perceived at any location of driver's hand.
US-2010-307900-A discloses an active skin for conformable tactile interface. In fact, such an artificial skin could be used, to realize some of mentioned above functionalities being applied as intelligent covering for the steering wheel. However, the concept and manufacturing of the artificial skin for the steering wheel is not free of flaws, especially linked with the propagation of mechanical energy of tactile stimuli to the skin receptors to compensate for disturbances caused by driving conditions, as well as variable threshold of receptors of the human skin to tactile stimuli, and testing vital parameters in the contact area.
Parameters of the human skin vary significantly and affected by many different factors of physical, physiological (humoral), and psychological nature, and by conditions of tactile stimulation.
Some efforts have already been undertaken to improve the conditions for propagation of mechanical energy of tactile stimuli to skin receptors (e.g., Arai F. et al. “Transparent tactile feeling device for touch-screen interface” Proc. of the 2004 IEEE Int. Workshop on Robot and Human Interactive Communication, 2004, 527-532, Weissman, A. W. “Modeling of Micro-scale Touch Sensations for use with Haptically Augmented Reality” MSc. Thesis, Rochester Inst. of Technology, Rochester, N.Y., USA, 2010, JP-2005-234704-A, U.S. Pat. No. 7,375,454-B, U.S. Pat. No. 8,362,882-B) by placing actuators in a direct contact with human skin (smart fabrics/e-textiles and coverings), through compensation/suppression of disturbances, external noise and surround vibrations by making an exact (easy distinguishable) waveform of stimuli in a specific location due to detection of tactile stimuli propagation to a destination field of contact (e.g., U.S. Pat. No. 8,378,797-B), or by observing the result of skin deformation (variations in skin strain) in the field of contact and adapting the applied magnitude of tactile stimuli (e.g., U.S. Pat. No. 7,077,015-B).
However, being deformed skin receptors might be blocked when e.g., fingers grip a rigid surface or fingertips froze, or protected with gloves. Even for levels of energy alterations which significantly exceed 24 dB above the skin sensitivity, the sensory threshold might be too high, by making the proposed solutions inefficient. Investigations into the mechanical impedance of the human skin have shown a nonlinear increase in stiffness when pressure was produced against the contact surface until a maximum skin indentation of approximately 3 mm (e.g., Mortimer B. J. P. et al. “Vibrotactile transduction and transducers” J. Acoust. Soc. Am., 2007, 121(5), 2970-2977).
Interaction through elastomeric material covering a stiff surface and with a density higher than human skin will squeeze the skin and increase the perceptual threshold by damping the response of skin receptors to tactile stimuli. Depending on a loss modulus, elastomeric materials can absorb energy of external vibration (e.g., US-2006-278034-A, EP-1733949-B) as well as applied stimuli by changing their meaning. On the other hand, the fluidic substance can mediate blood flow pulse vibrations to the sensor and vibration stimuli (aka feedback) to the driver's skin.
There have been some inventions made for improving the sensory parameters of touch, in particular, to lower the threshold of skin receptors. For example, a bias signal may be applied to the skin before the informative (tactile) stimuli (e.g., U.S. Pat. No. 5,782,873-A, U.S. Pat. No. 6,032,074-A, U.S. Pat. No. 8,040,223-B, US-2009-128305-A). However, such an approach does not eliminate the problems of signal propagation to tactile receptors for sub-sensory vibrational stimuli that has to change sensitivity of the skin within the predefined time interval as well as transmission of physiological signals from the hand skin to sensors.
The coverings, which have a density of the surface of interaction similar to the density of hypodermis of the human skin, that is typically 1100 kg/m3 (e.g., Gennisson, J.-L. et al. “Assessment of Elastic Parameters of Human Skin Using Dynamic Elastography” IEEE Trans. on Ultrasonics, Ferroelectrics, and Freq. Control, 2004, 51(8), 980-989) and regulated viscosity of the fluidic substance, could be more universal technical solution for improving the sensory parameters of touch and haptic/tactile information imaging. Wherein, viscosity of the fluidic (magneto-/electro-rheological) substance can be altered with an electrical current or magnetic field to adapt for recording vital parameter such as arterial pulses.
By taking into consideration all mentioned above requirements and techniques we disclose a cost effective arrangement of self-sensing transducers (e.g., US-2010-164324-A) operating as actuators and sensors through elastomeric covering of the steering wheel filled in with fluidic substance mediating transmission of vital signs and haptic events.